/*
 * @(#)ResourceFinder.java
 *
 * Copyright 2003-2006 Sun Microsystems, Inc. All Rights Reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *
 *   1. Redistribution of source code must retain the above copyright notice,
 *      this list of conditions and the following disclaimer.
 * 
 *   2. Redistribution in binary form must reproduce the above copyright
 *      notice, this list of conditions and the following disclaimer in the
 *      documentation and/or other materials provided with the distribution.
 *
 * Neither the name of Sun Microsystems, Inc. or the names of contributors may
 * be used to endorse or promote products derived from this software without
 * specific prior written permission.
 * 
 * This software is provided "AS IS," without a warranty of any kind. ALL
 * EXPRESS OR IMPLIED CONDITIONS, REPRESENTATIONS AND WARRANTIES, INCLUDING
 * ANY IMPLIED WARRANTY OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE
 * OR NON-INFRINGEMENT, ARE HEREBY EXCLUDED. SUN MICROSYSTEMS, INC. ("SUN")
 * AND ITS LICENSORS SHALL NOT BE LIABLE FOR ANY DAMAGES SUFFERED BY LICENSEE
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package org.wso2.balana.finder;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.wso2.balana.ctx.EvaluationCtx;

import org.wso2.balana.attr.AttributeValue;

import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;

/**
 * This class is used by the PDP to handle resource scopes other than Immediate.
 * In the case of a scope of Children or Descendants, the PDP needs a list of
 * Resource Ids to evaluate, each of which will get its own Result. Like the
 * PolicyFinder, this is not tied in any way to the rest of the PDP code, and
 * could be provided as a stand-alone resource.
 * <p>
 * This class basically is a coordinator that asks each module in turn if it can
 * handle the given identifier. Evaluation proceeds in order through the given
 * modules, and once a module returns a non-empty response (whether or not it
 * contains any errors or only errors), the evaluation is finished and the
 * result is returned. One of the issues here is ordering, since a given
 * resource may look to several modules like something that they can handle. So,
 * you must be careful when assigning to ordering of the modules in this finder.
 * <p>
 * Note that in release 1.2 the interfaces were updated to include the
 * evaluation context. In the next major release the interfaces without the
 * context information will be removed, but for now both exist. This means that
 * if this finder is called with the context, then only the methods in
 * <code>ResourceFinderModule</code> supporting the context will be called (and
 * likewise only the methods without context will be called when this finder is
 * called without the context). In practice this means that the methods with
 * context will always get invoked, since this is what the default PDP
 * implementation calls.
 * 
 * @since 1.0
 * @author Seth Proctor
 */
public class ResourceFinder {

	// the list of all modules
	private List allModules;

	// the list of child modules
	private List childModules;

	// the list of descendant modules
	private List descendantModules;

	// the logger we'll use for all messages
	private static Log logger = LogFactory.getLog(ResourceFinder.class);

	/**
	 * Default constructor.
	 */
	public ResourceFinder() {
		allModules = new ArrayList();
		childModules = new ArrayList();
		descendantModules = new ArrayList();
	}

	/**
	 * Returns the ordered <code>List</code> of
	 * <code>ResourceFinderModule</code>s used by this class to find resources.
	 * 
	 * @return a <code>List</code> of <code>ResourceFinderModule</code>s
	 */
	public List getModules() {
		return new ArrayList(allModules);
	}

	/**
	 * Sets the ordered <code>List</code> of <code>ResourceFinderModule</code>s
	 * used by this class to find resources. The ordering will be maintained.
	 * 
	 * @param modules
	 *            a code>List</code> of <code>ResourceFinderModule</code>s
	 */
	public void setModules(List modules) {
		Iterator it = modules.iterator();

		allModules = new ArrayList(modules);
		childModules = new ArrayList();
		descendantModules = new ArrayList();

		while (it.hasNext()) {
			ResourceFinderModule module = (ResourceFinderModule) (it.next());

			if (module.isChildSupported())
				childModules.add(module);

			if (module.isDescendantSupported())
				descendantModules.add(module);
		}
	}

	/**
	 * Finds Resource Ids using the Children scope, and returns all resolved
	 * identifiers as well as any errors that occurred. If no modules can handle
	 * the given Resource Id, then an empty result is returned.
	 * 
	 * @param parentResourceId
	 *            the root of the resources
	 * @param context
	 *            the representation of the request data
	 * 
	 * @return the result of looking for child resources
	 */
	public ResourceFinderResult findChildResources(
			AttributeValue parentResourceId, EvaluationCtx context) {
		Iterator it = childModules.iterator();

		while (it.hasNext()) {
			ResourceFinderModule module = (ResourceFinderModule) (it.next());

			// ask the module to find the resources
			ResourceFinderResult result = module.findChildResources(
					parentResourceId, context);

			// if we found something, then always return that result
			if (!result.isEmpty())
				return result;
		}

		// no modules applied, so we return an empty result
		logger.info("No ResourceFinderModule existed to handle the "
				+ "children of " + parentResourceId.encode());

		return new ResourceFinderResult();
	}

	/**
	 * Finds Resource Ids using the Children scope, and returns all resolved
	 * identifiers as well as any errors that occurred. If no modules can handle
	 * the given Resource Id, then an empty result is returned.
	 * 
	 * @deprecated As of version 1.2, replaced by
	 *             {@link #findChildResources(AttributeValue,EvaluationCtx)}.
	 *             This version does not provide the evaluation context to the
	 *             modules, and will be removed in a future release.
	 * 
	 * @param parentResourceId
	 *            the root of the resources
	 * 
	 * @return the result of looking for child resources
	 */
	public ResourceFinderResult findChildResources(
			AttributeValue parentResourceId) {
		Iterator it = childModules.iterator();

		while (it.hasNext()) {
			ResourceFinderModule module = (ResourceFinderModule) (it.next());

			// ask the module to find the resources
			ResourceFinderResult result = module
					.findChildResources(parentResourceId);

			// if we found something, then always return that result
			if (!result.isEmpty())
				return result;
		}

		// no modules applied, so we return an empty result
		logger.info("No ResourceFinderModule existed to handle the "
				+ "children of " + parentResourceId.encode());

		return new ResourceFinderResult();
	}

	/**
	 * Finds Resource Ids using the Descendants scope, and returns all resolved
	 * identifiers as well as any errors that occurred. If no modules can handle
	 * the given Resource Id, then an empty result is returned.
	 * 
	 * @param parentResourceId
	 *            the root of the resources
	 * @param context
	 *            the representation of the request data
	 * 
	 * @return the result of looking for descendant resources
	 */
	public ResourceFinderResult findDescendantResources(
			AttributeValue parentResourceId, EvaluationCtx context) {
		Iterator it = descendantModules.iterator();

		while (it.hasNext()) {
			ResourceFinderModule module = (ResourceFinderModule) (it.next());

			// ask the module to find the resources
			ResourceFinderResult result = module.findDescendantResources(
					parentResourceId, context);

			// if we found something, then always return that result
			if (!result.isEmpty())
				return result;
		}

		// no modules applied, so we return an empty result
		logger.info("No ResourceFinderModule existed to handle the "
				+ "descendants of " + parentResourceId.encode());

		return new ResourceFinderResult();
	}

	/**
	 * Finds Resource Ids using the Descendants scope, and returns all resolved
	 * identifiers as well as any errors that occurred. If no modules can handle
	 * the given Resource Id, then an empty result is returned.
	 * 
	 * @deprecated As of version 1.2, replaced by
	 *             {@link #findDescendantResources(AttributeValue,EvaluationCtx)}
	 *             . This version does not provide the evaluation context to the
	 *             modules, and will be removed in a future release.
	 * 
	 * @param parentResourceId
	 *            the root of the resources
	 * 
	 * @return the result of looking for child resources
	 */
	public ResourceFinderResult findDescendantResources(
			AttributeValue parentResourceId) {
		Iterator it = descendantModules.iterator();

		while (it.hasNext()) {
			ResourceFinderModule module = (ResourceFinderModule) (it.next());

			// ask the module to find the resources
			ResourceFinderResult result = module
					.findDescendantResources(parentResourceId);

			// if we found something, then always return that result
			if (!result.isEmpty())
				return result;
		}

		// no modules applied, so we return an empty result
		logger.info("No ResourceFinderModule existed to handle the "
				+ "descendants of " + parentResourceId.encode());

		return new ResourceFinderResult();
	}

}
